Ignition and control system for gas burners

ABSTRACT

The system comprises a burner, a glow igniter, two series flow connected biased closed solenoid valves and a normally closed sensor switch. The first valve has two windings series connected across a power source, one winding having high impedance limits current flow and prevents opening of the valve. The other winding having low impedance is series connected with the igniter across the power source through a sensor switch causing the first valve to open and the igniter to heat. The second valve has a single winding in parallel with the sensor switch. When the igniter reaches ignition temperature, the sensor switch opens. This energizes the second valve winding and opens the valve and reduces current flow through the igniter and through the low impedance valve winding, which in conjunction with the high impedance winding holds the first valve open but will not pull it open. Burner flame maintains the sensor switch open.

v United States Patent [19 Fernstrom [111' 3,807,933 [451 Apr. 30, 1974IGNITION AND CONTROL SYSTEM FOR GAS BURNERS [75] Inventor:' Carl F.Femstrom, St. Louis, Mo.

[73] Assignee: Emerson Electric Co., St. Louis, Mo.

[22] Filed: Jan. 8, 1973 [21] Appl. No.: 321,739

[52] US. Cl. 431/66 [51] Int. Cl. F23n 5/00 [58] Field of Search 431/66,67

[56] References Cited UNITED STATES PATENTS I 3,620,659 11/1971 Fox 431/66 3,597,139 8/1971 Elders 431/66 Primary ExaminerEdward G. FavorsAttorney, Agent, or Firm-Charles E. Markham [57] ABSTRACT The systemcomprises a burner, a glow igniter, two series flow connected biasedclosed solenoid valves and a normally closed sensor switch. The firstvalve has two windings series connected across a power source, onewinding having high impedance limits current flow and prevents openingof the valve. The other winding having low impedance is series connectedwith the igniter across the power source through a sensor switch causingthe first valve to open and the igniter to heat. The second valve has asingle winding in parallel with the sensor switch. When the igniterreaches ignition temperature, the sensor switch opens.

.This energizes the second valve winding and opens the valve and reducescurrent flow through the igniter and through the low impedance valvewinding, which in conjunction with the high impedance winding holds thefirst'valve open but will not pull it open. Burner flame maintains thesensor switch open.

6 Claims, 1 Drawing Figure generating IGNITION AND CONTROL SYSTEM FORGAS BURNERS This invention relates generally to gas burner ignition andcontrol systems, and particularly to those systems employing a glowigniter with sensor means operative to initiate the flow of gas to theburner only when the igniter has reached a gas ingition temperature andoperative to maintain the flow thereafter only so long as burner flameis present.

Systems of this general character employing two solenoid operated fuelvalves connected in series in the fuel supply line are shown anddescribed in US. Pat. Nos. 3,589,846 and 3,597,139.

I An object of this invention is to provide a generally new and improvedsystem'of this kind which provides assurance that neither of the seriesflow connected valves will be opened unless electrical current isflowing through the igniter.

A further object is to provide a system of this kind in which at leastone of the series flow connected solenoid valves will not open unlessthe current flow through the igniter is sufficient to result in itsbeing heated to ignition temperature.

Further objects and advantages will appear from the tion in response tothe radiant energy of the burner flame when the igniter drops belowignition temperature.

following description of a preferred form of the invention when read inconnection with the accompanying drawing.

The single FIGURE of the drawing is a diagrammatic representation of aburner ignition and control system constructed in accordance with thepresent invention.

Referring to the drawing, first and second biased closed solenoidoperated valves 10 and 12 are connected in series in a fuel supplyconduit 14 leading to a burner 16.. First valve 10 has two solenoidwindings l8 and 20 connected in series with a thermostat 26 acrossterminals 22 and 24 of a power supply having a predetermined nominalvoltage. Winding 18 is also connected in series with a glow igniter 28and a solenoid winding 30 of the second valve 12 across power supplyterminals 22 and 24 through thermostat 26.

A normally closed sensor switch 32 connected across the solenoid winding30 shunts this'winding so that when sensor switch 32 is closed onlysolenoid winding 18 and glow igniter 28 are effectively series connectedacross the power supply. Solenoid windings 18 and 20 of valve 10 arewound on the same spool surrounding the solenoid plunger, and bothgenerate flux tending to pull the valve 10 open when they are energized.The winding 20 has high impedance and is not capable of sufficient fluxalone to open valve 10 against its bais. Series connected winding 18, onthe other hand, has quite low impedance. Sufficient current flow throughseries connected windings 18 and 20 to effect opening of'valve 10 isprecluded, however, by the impedance of winding 20.

Glow igniter 28 requires a predetermined current flow therethrough toinsure that it will attain ignition temperature, and solenoid winding 18is so designed as to require substantially thispredetermined currentflow therethrough to develop in conjunction with winding 20 sufficientflux to pull open valve 10. The normally closed sensor switch 32 isdisposed with relation to igniter 28 so as to respond to the radiantenergy thereof and open when the igniter reaches gas ignitiontemperature. Sensor switch 32 is also disposed with relation to theburner 16 so as to be maintained in an open posi- The solenoid winding30 of valve 12 is designed so as to pull open the valve when it becomeseffectively connected in series with solenoid winding 18 and igniter 28upon opening of the shunting sensor switch 32. The total impedance ofseries connected solenoid winding 18, glow igniter 28, and solenoidwinding 30 is such that current flow through igniter 28 and winding 18is reduced considerably when sensor switch 32 opens. This reducedcurrent flow through winding 18 results in the reduction of fluxgenerated thereby to a value below that which, even in conjunction withflux generated in high impedance winding 20, is sufficient to pull openvalve 10 against its bias. However, the flux jointly developed by thesetwo windings under these conditions is sufficient to hold valve 10 inopen position. The reduction in current flow through igniter 28, whichoccurs when sensor switch 32 opens, also results in a drop in thetemperature of the igniter to a point below that which will maintainsensor switch 32 in an open position. The switch 32 will, however,remain open under these conditions in response to the radiant energy ofburner flame if it exists.

It is essential, of course, that the igniter temperature remainsufficiently high to ignite gas for the short period of time requiredfor gas to flow from the valves to the burner following the opening ofsensor switch 32. To meet this requirement, a glow igniter havingsufficient mass to retain an ignition temperature for this short periodmay be employed, or the sensor switch may be calibrated to open at sometemperature above ignition temperature, or both of these expedients maybe employed.

NORMAL OPERATION When thermostat 26 closes in response to a requirementfor burner operation, low impedance winding 18 and igniter 28 are seriesconnected across the power source through closed sensor switch 32. Thiscauses heating of the igniter 28 and the opening of valve 10. Whenigniter 28 reaches gas ignition temperature, the sensor switch 32 opens.The opening of sensor switch 32 places solenoid winding 30 in serieswith winding 18 and igniter 28, causing valve 12 to open. Gas now flowsto burner 16 and is ignited.

The opening of sensor switch 32 also results in a considerable reductionin current flow through igniter 28 and, consequently, a considerabledrop in the temperature thereof, but the radiant energy of the nowexisting burner flame maintains the sensor switch open. The burner nowcontinues to operate normally until the thermostat 26 opens. Opening ofsensor switch 32 further results in such reduction of current flowthrough winding 18 so that the flux now jointly developed in windings 18and 20 is sufficient only to hold valve 10 open and not sufficient topull it open.

ABNORMAL CONDITIONS If the sensor switch 32 fails to close during aperiod of inoperation of the burner, the valve 10 will not open uponsubsequent closure of the thermostat because of the impedance of winding30, which would be in series with winding 18 and igniter 28 under theseconditions.

Even though sensor switch 32 is closed, valve will not open upon closureof the thermostat unless sufficient current is flowing through winding18 and the series connected igniter 28 to result in its attainingignition temperature. lnsufficient current flow may occur due to lowpower supply voltage, a local area of high resistance to the igniter, orpoor lead connections.

If during normal operation of the burner the electrical power supply isinterrupted, causing valves 10 and 12 to close and the burner flame tobe extinguished, valve 10 will not reopen upon a resumption of poweruntil sensor switch 32 cools and closes. This provision prevents theflow of unburned gas from the burner if power is restored during theperiod required for the sensor switch to cool and close and for theigniter to again reach ignition temperature.

By requiring that current flow through igniter 28 and series connectedsolenoid winding 18 be sufficient to result in the igniter attainingignition temperature before valve 10 is opened, an unsafe condition isprevented, which may otherwise occur if sensor switch 32 opens inresponse to an igniter temperature below that required to ignite gas.

I claim:

1. In an ignition and control system for gas burners, a burner, firstand second biased closed solenoid operated valves arranged in series ina gas supply conduit leading to said burner, a solenoid winding for eachof said valves, a glow igniter, and a normally closed sensor switchwhich opens when said igniter reaches gas ignition temperature and ismaintained open thereafter by burner flame, circuit connections seriesconnecting said first valve winding, said glow igniter, and said secondvalve winding across a power source and circuit connections connectingsaid sensor switch across said second valve winding, thereby shunting itwhen said switch is closed, said first valve winding being operative toeffect opening of said first valve only when said sensor switch isclosed and the current flow through said first valve winding and saidseries connected igniter is sufficient to heat said glow igniter to gasignition temperature, and said second valve winding being operative toopen said second valve when said sensor switch opens.

2. The ignition and control device claimed in claim 1 in which thecurrent flow through said first valve winding and said igniter isreduced below that required to open said first valve and below thatrequired to maintain said igniter at ignition temperature when saidsensor switch opens, and in which said sensor switch is maintained inopen position jointly by burner flame and the heat of said igniter,

3. In an ignition and control system for gas burners, a burner, firstand second biased closed solenoid operated valves arranged in series ina gas supply conduit leading to said burner, a high impedance solenoidwinding and a low impedance solenoid winding for said first valveconnected in series across a power supply, a solenoid winding for saidsecond valve, a glow igniter, and a normally closed sensor switch whichopens when said igniter reaches gas ignition temperature, circuitconnections connecting said first valve low impedance winding, said glowigniter, and said second valve winding in series across said powersupply and in parallel with said high impedance winding, circuitconnections connecting said sensor switch across said second valvewinding thereby shunting it when said switch is closed, said seriesconnected high and low impedance windings being jointly capable ofopening said first valve only when said sensor switch is closed and whensufficient current is flowing through said low impedance winding andsaid series connected igniter to heat said igniter to gas ignitiontemperature, and said second valve being opened when said sensor switchopens, said series connected high and low impedance windings beingcapable of holding said first valve open when said sensor switch isopen, and said sensor switch being maintained in open position by burnerflame.

4. The ignition and control device claimed in claim 3 in which the totalimpedance of the series connected first valve low impedance winding, theglow igniter, and the second valve winding is such when said sensorswitch opens as to result in a substantial reduction in the temperatureof said igniter.

5. The ignition and control device claimed in claim 3 in which saidfirst valve low impedance winding has relatively few turns and in whichthe total impedance of the series connected low impedance winding, theglow igniter, and the second valve winding is such when the sensorswitch opens that said low impedance winding provides only a relativelysmall portion of the magnetic force required to hold said first valveopen.

6. In an ignition and control system for gas burners, a burner, anelectrical power source, first and second biased closed solenoidoperated valves arranged in series in a gas supply conduit leading tosaid burner, a solenoid winding for each of said valves, a glow igniter,and a normally closed sensor switch which opens when said igniterreaches ignition temperature and is thereafter maintained open by burnerflame, circuit connections connecting said first valve winding in serieswith said glow igniter and with said second valve winding across saidpower source, and circuit connections connecting said sensor switchacross said second valve winding thereby shunting it when said switch isclosed, a second solenoid winding for said first valve, said windingsfor said first valve being series connected across said power source andbeing jointly operative to effect opening of said first valve only whensaid sensor switch is closed and when sufficient current is flowingthrough said igniter to heat it to ignition temperature,

and said second valve winding being operative to open said second valveonly when said sensor switch opens, the total impedance of said seriesconnected first and second valve windings and said igniter being suchwhen said sensor switch is open that the current flow through said firstvalve winding is reduced below that required to hold said first valveopen and both windings of said first valve being jointly operative tohold said first valve open when sensor switch opens.

* 1 t I 1F

1. In an ignition and control system for gas burners, a burner, firstand second biased closed solenoid operated valves arranged in series ina gas supply conduit leading to said burner, a solenoid winding for eachof said valves, a glow igniter, and a normally closed sensor switchwhich opens when said igniter reaches gas ignition temperature and ismaintained open thereafter by burner flame, circuit connections seriesconnecting said first valve winding, said glow igniter, and said secondvalve winding across a power source and circuit connections connectingsaid sensor switch across said second valve winding, thereby shunting itwhen said switch is closed, said first valve winding being operative toeffect opening of said first valve only when said sensor switch isclosed and the current flow through said first valve winding and saidseries connected igniter is sufficient to heat said glow igniter to gasignition temperature, and said second valve winding being operative toopen said second valve when said sensor switch opens.
 2. The ignitionand control device claimed in claim 1 in which the current flow throughsaid first valve winding and said igniter is reduced below that requiredto open said first valve and below that required to maintain saidigniter at ignition temperature when said sensor switch opens, and inwhich said sensor switch is maintained in open position jointly byburner flame and the heat of said igniter.
 3. In an ignition and controlsystem for gas burners, a burner, first and second biased closedsolenoid operated valves arranged in series in a gas supply conduitleading to said burner, a high impedance solenoid winding and a lowimpedance solenoid winding for said first valve connected in seriesacross a power supply, a solenoid winding for said second valve, a glowigniter, and a normally closed sensor switch which opens when saidigniter reaches gas ignition temperature, circuit connections connectingsaid first valve low impedance winding, said glow igniter, and saidsecond valve winding in series across said power supply and in parallelwith said high impedance winding, circuit connections connecting saidsensor switch across said second valve winding thereby shunting it whensaid switch is closed, said series connected high and low impedancewindings being jointly capable of opening said first valve only whensaid sensor switch is closed and when sufficient current is flowingthrough said low impedance winding and said series connected igniter toheat said igniter to gas ignition temperature, and said second valvebeing opened when said sensor switch opens, said series connected highand low impedance windings being capable of holding said first valveopen when said sensor switch is open, and said sensor switch beingmaintained in open position by burner flame.
 4. The ignition and controldevice claimed in claim 3 in which the total impedance of the seriesconnected first valve low impedance winding, the glow igniter, and thesecond valve winding is such when said sensor switch opens as to resultin a substantial reduction in the temperature of said igniter.
 5. Theignition and control device claimed in claim 3 in which said first valvelow impedance winding has relatively few turns and in which the totalimpedance of the series connected low impedance winding, the glowigniter, and the second valve winding is such when the sensor switchopens that said low impedance winding provides only a relatively smallportion of the magnetic force required to hold said first valve open. 6.In an ignition and control system for gas burners, a burner, anelectrical power source, first and second biased closed solenoidoperated valves arranged in series in a gas supply conduit leading tosaid burner, a solenoid winding for each of said valves, a glow igniter,and a normally closed sensor switch which opens when said igniterreaches ignition temperature and is thereafter maintained open by burnerflame, circuit connections connecting said first valve winding in serieswith said glow igniter and with said second valve winding across saidpower source, and circuit connections connecting said sensor switchacross said second valve winding thereby shunting it when said switch isclosed, a second solenoid winding for said first valve, said windingsfor said first valve being series connected across said power source andbeing jointly operative to effect opening of said first valve only whensaid sensor switch is closed and when sufficient current is flowingthrough said igniter to heat it to ignition temperature, and said secondvalve winding being operative to open said second valve only when saidsensor switch opens, the total impedance of said series connected firstand second valve windings and said igniter being such when said sensorswitch is open that the current flow through said first valve winding isreduced below that required to hold said first valve open and bothwindings of said first valve being jointly operative to hold said firstvalve open when sensor switch opens.